The poly(ethylene glycol) assisted preparation of NH4TiOF3 mesocrystals and their topotactic conversion to TiO2

Poly(ethylene glycols) with different molecular weights were used to prepare NH4TiOF3 mesocrystals. The use of PEG-1000, -10 000, or -20 000 produced NH4TiOF3 mesocrystals whereas, PEG-4500 produced TiO2 (anatase) in nanoparticulate form. The shapes and the crystal structures of NH4TiOF3 mesocrystals formed with PEGs are similar to those obtained with the Brij family of nonionic surfactants. The conversion of NH4TiOF3 mesocrystals prepared with PEG-20 000 to TiO2 (anatase) mesocrystals by heat treatment or washing with boric acid was also studied. The TiO2 mesocrystals retained the crystallographical orientation of the parent NH4TiOF3 mesocrystals and the apparent average sizes of the nanoparticles are between several and tens of nanometers.